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Anyone have the pinout for the iMac revs A/B mezzanine/perch slot? Or any other mezzanine slot info? I Googled ’til my eyes bled but found nothing other than references to the Game Wizard and Formac’s scsi adapter.

I have the crazy notion to add a PCcard cage, arguably the most useful of all upgrade slots short of an actual PCI slot.

Dan K
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I am new to this site and tried to reply to this post, but it was too old. I do indeed have the pinouts to the mezzanine connector (or at least the better part of half of them. The story is that this connector was electrically identical to the personality slot on some earlier Macs. The difference is that the pin count was off bya bout 16 or so pins. I was able to get my hand on a IProRaid TV card (by Formac) and get the specs for some of the chips on the board. By using a continutiy tester, I was able to reverse engineer the connector to the chips. The problem is that the chips only utilized the lower 32 bits of the PCI format. The connector will support a full 64 bit PCI connection if you can figure out the remaining pins. I never had much luck beyond this point. What I do have is a decent (albeit hardcopy) documentation of the pinouts with enough detail that one should be able to construct a 32 bit PCI card for this slot. I have the part numbers needed for the connector as well. The caveat is that some of the crucial pins for the Device select and interupt are questionable (but marked as such). It is a decent start for the brave. I will try to dig this info up from my archives and package it.

Incidentally, I did get some part numbers on PC Card slots and supported chipsets as well. What stopped me from pursuing this project was time and money, but what research I have is yours if you would like.

I don't know where you got the idea that slot has 64 bit PCI available on it. It doesn't. The iMac in question uses the MPC106 PCI controller that only outputs 32/33 or 32/66. The Blue and White G3's had a PCI-PCI bridge that took 32/66 from the MPC106 and turned into 64/33 slots.

I got the idea from information I read about the port at the time. I never did go back and verify the functionality of the on board PCI controller to establish what it supported in terms of 32 v 64 bit. But I can vouch for the following:
- 64 bit PCI has 198 pins (per standard), but neglecting the reserved bits and eliminating the redundant bits (i.e. appx 40 pins as ground, including the 'keys'), there are 112 unique pins. A similar situation is true with the 32 bit space, having about 75 unique pins. Your point about the functionality of the MPC aside, this is interesting to know.
- out of 160 pins, I know 94 of the pins from verifying continuity between chips and the connector on an iProRaid TV card.
- I am missing 16 pins to account for the full set within the 32 bit space (but this includes things like 'Test Logic Reset', 'Test Clock', Interupts B, C, and D, and a few others). Unfortunatly, 'System Error', 'Parity Error', and Initialization Device Select' are included in this.
- If one wanted to place the chasis for a cardbus inside of an iMac, the native hole on the 233 is a near perfect match to accomodate a type 3 card.
- the bus architecture of the early iMacs and 199 G3 Series Powerbooks is virtually identical with the differences being the models on certain chipsets (i.e. USB, video, and Ethernet). But how things are arranged around the Padington is the same.

It stands to reason, and this is where Dan K's idea was sound and where I was trying to go until I gave up, that by utilizing the mezz slot and planting a PCI1210 or PCI1220 (and a few other minor parts required for use of these chips) onto a custom mezz card with a cardbus chasis, one could provide cardbus functionality on an early iMac. Alternaltively, one could hang a DVD decoder or secondary video card or firewire port off of a mezz card (practicality of each choice aside).

Now that I have my notes dug back out, I may try to find time to reverse engineer these other pins off of the motherboard. I am more than happy to share what pins I do know if anyone is interested. Because all of what I did was from the card-side, I left it open that the connector could be full 64 bit. With your info about the MPC, it means that the info I have is much closer to complete than I thought. Perhaps those other bits include some audio pins and perhaps some of the ancillary pins from the Rage IIc (which could be augmented with an optional TV tuner (per chip specs) when an assisting chip was added. I would love to get some insider info on what Apple intended with this port!

The original purpose of that port was to connect a logic analyzer and quickly diagnose board problems. It was intended to make servicing the boards easier. It was never at any time intended for an upgrade card, and thus, the PCI loads were calculated for that board with the intention of no real PCI loads being present.

The rest of the pins are used for various signals on the board. Just because there are more pins, or enough pins for 64 bit PCI, does not make it so. That's only wishful thinking. Motorola no longer supports the MPC106, and has sold the line to Tundra. Here is the info on the part:

the bus architecture of the early iMacs and 199 G3 Series Powerbooks is virtually identical with the differences being the models on certain chipsets (i.e. USB, video, and Ethernet). But how things are arranged around the Padington is the same

The Wallstreet, PDQ, 101, Beige G3, B&W G3, and 1st gen iMacs all used the MPC106 architecture. Of which Wallstreet and Beige G3 used Heathrow, and the rest used Paddington. Both are PCI devices. Such commonality of design is quite common within generations of products.

Not trying to argue, I just was answering the question as to where I got the idea from. Thanks for the link for the MPC, I can't find that I ever had this info in my notes, but they are going on three years old and have been through 3 residential moves during that time (still looking for some other things too

You mention the loads on the PCI bus - I am not sure what the spec tolerances are, but I know that the iProRaidTV actually had two PCI devices on it (the tuner and the SCSI controller). I heard mixed results on how successful these cards were. I am sure the system could successfully tolerate a single PCI device (stablely) long term. Two is a bit much if it could be possible to construct a PC Card adapter for the slot.

My plan at this point is to try to figure out the missing pins for the 32 bit set. I got the pin outs for the MPC, but it is so tight I do not think I will have much luck with this tactic. I am trying to get ATI to give me the pinouts for the Rage IIc. It is a little bit bigger and should be easier to hit with a probe. If anyone has the pinouts for this, let me know.

Thank you Doug for reviving this topic, I've read this discussion with great interest! I had previously come across your mez-slot info, but hadn't had the time to do much followup.

Mac-supported cardbus PCI cards are available, I'm wondering about the possibility of having their makers produce an identical board with a mez connector instead of PCI? Hmmmm . . .

Dr. Bob wrote:

Quote:

The original purpose of that port was to connect a logic analyzer and quickly diagnose board problems. It was intended to make servicing the boards easier. It was never at any time intended for an upgrade card, and thus, the PCI loads were calculated for that board with the intention of no real PCI loads being present.

These details are news to me! Please tell us Dr. Bob of how you came to hold this interesting and useful knowledge, and if I may be so bold, what the heck else do you know about the mez slot?

I've not seen the above info before, so naturally I'm excited to know of someone (that being Dr. Bob) who knows more.

These details are news to me! Please tell us Dr. Bob of how you came to hold this interesting and useful knowledge, and if I may be so bold, what the heck else do you know about the mez slot?

This friday is my last day of just shy of 6 years at apple. Most of our boards have diagnostic ports, but after people started using the mez slot in the iMac, they deleted the connectors and opened the circuit lines going to them. As boards got faster, signal integrity later demanded it anyway.

You mention the loads on the PCI bus - I am not sure what the spec tolerances are, but I know that the iProRaidTV actually had two PCI devices on it (the tuner and the SCSI controller). I heard mixed results on how successful these cards were. I am sure the system could successfully tolerate a single PCI device (stablely) long term. Two is a bit much if it could be possible to construct a PC Card adapter for the slot.

The term "loads" refers to how much current the receiving data devices can draw from the source transmitter before voltage drops to unacceptable levels. Usually, once a board is done in design, (unless it has slots) resistors are added to the data lines to make the signal integrity higher and performance better, at the expense of being able to change the loads better. So in the case of a diagnostic port, the logic analyzer draws an incredibly small amount of power, far less than a normal PCI device.

To add to the bus, upgrade card companies are using buffers to amplify the PCI signals without drawing too much current. However, this approach does weaken signal integrity, and also reduces performance.

Quote:

My plan at this point is to try to figure out the missing pins for the 32 bit set. I got the pin outs for the MPC, but it is so tight I do not think I will have much luck with this tactic. I am trying to get ATI to give me the pinouts for the Rage IIc. It is a little bit bigger and should be easier to hit with a probe. If anyone has the pinouts for this, let me know.

You really need the schematics, but those aren't available. I'm surprised ATI doesn't have the pinout on their web site. The rage Pro is pin compatible so check it too.

...and for the hobbyists, like Dan and myself, could an offline discussion provide more room for any grey areas to be encroached upon? Mentoring, in any form or fashion would be highly appreciated. My background is in Physics and Electronics (but not PC design).

ATI has been rather tight-lipped about their pinouts. This is not the first time I have tried to get information like this from them. I plan to call someone tomorrow (vice another email).

My assumption about the loads is that a device (such as a PC Card add-on) would be manageable by the system as it is only one device on the bus (compared to the IProRaid, which had two). (Yes, I am rather attached to this idea.)

This is what I DO know at this time...
(caveat: This came from my reverse engineering an iProRaidTV card - I have not yet tried to check any of this from the motherboard side of things but plan to soon.)

For better or worse, this is what I know and stand by from my own hacking around. If you (Dr. Bob or Dan) or any other readers would like to correct/augment this list, either reply to the post or to my email at .

Also, the/a manufacturer for the connector (and subsequent mates to it is Molex and the part number is 52760-1609. Ther are only a few cardbus chasis that are designed for type 3 cards and will fit in the space requirements of the internal as well as the side port. These are available through distributors like Allied. I cannot find my notes on these so no part numbers right now - besides, there may be some better fitting ones that what I found at the time. The controller for the cardbus on the 1999 G3 Series laptops was a TI PCI1120, which was discontinued and replace with a pin-compatible update (PCI1220). This may have been subsequently replace by a new chip, but the info should be readily available on the TI site as this is where I got the tech specs and pinouts for the aforementioned.

DoctorMemeory has a Lombard for sale. It is $300 obo. The bus seems bad, but othe parts seem okay. This is a good machine for canablaizing to get the cardbus controller and cage off of and even the LCD per my PM the other day.

Having recently traded some iBook stuff to astrorob for a new analog board, I am planning on getting this machine back up and running. If anyone has a Lombard/Pismo mobo for trade/sale, please let me know.

I am hoping to get parts so I can play around with this in my free time.

Would kill to have an iProRaidTV card.

I do not expect to get too far, but we all have our White Whales to pursue...

miniPCI is, but the pins are all wrong and since mezz, like PERCH, is a superset, there is of course the addition of some other things which feed directly to the Rage chip as well as to sound.

My original idea was to attempt to build a cardbus accessory for the iMac - the block architecture is the same as that of the Lombard, indicating that the concept has validity. Using the same TI components would mean no custom code. The opening on the side of the Rev A (the "mezz panel") is the perfect size for a type 3 card. The two small notches on the lower left of the opening add to the notion. I did some basic research at the time and had not fully settled on the right cage but I liked the idea and had some favs.

Lately, having some time, I thought about this and dragged my stuff out.

I have the all but two of the pins I need to make Cardbus work, but now having waited too long, the chips are most likely not to be found without pulling them off a laptop that happens to have what I need (dead Lombard/Pismo).

I still come back to the iProRaid TV - this was a tight little card but had some other wonderful possibilities based on my own inspection of one of these, not the least of which was the possibility of an internal SCSI bus (nevermind where one would put an internal SCSI drive...)

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